1. Field of the Invention
This invention relates to photographic film printers and particularly to a programmable exposure control device for use on film printers.
2. Description of the Prior Art
Photographic film printers are widely used in the motion picture industry for the improvement of a photographed scene with respect to image density, composition, color balance and the like. More advanced film printers have been provided for creating various special effects such as reverse action, double exposures, fade-ins, fade-outs, lap dissolves, and many other special optical effects as well as color balance corrections from film originally photographed on location or in the studio by conventional camera techniques.
When printing preprint film onto raw stock, it is often desirable that scenes be frequently faded out, faded in, or otherwise changed to create special effects. For example, transition from one scene to the next is often accomplished by fading out the first scene and fading in the following scene. These fades also can be made to occur within the same length of printed film so as to form what is commonly known as a lap dissolve.
Fades or dissolves of this type are conventionally accomplished by a conventional fader which comprises a device having movable vanes, capable of progressively varying the intensity of the printing beam at the film exposure aperture. To effect fade-outs, these vanes are moved together at a controlled rate to gradually eclipse the printing beam. Conversely, in fade-ins, the vanes are gradually separated so that the printing beam, which is initially entirely blocked out at the printing aperture, is gradually increased in intensity. Automation in film printing operations has greatly increased film printing speeds, and it therefore has been necessary that faders be automatically controlled in synchronism with the passage of the film through the printer so that fades will automatically occur at preset rates and at preselected positions or frames of the preprint film. Heretofore, automatic faders were capable of effecting fades only at a single predetermined rate which was a compromise rate for a limited number of film types. However, most modern films have exposure characteristics which are not linear and the exposure characteristics vary widely between different film compositions. Therefore, it is desirable to provide a fader having the ability to progressively vary the intensity of the printing beam at a particular nonlinear rate in accordance with the exposure characteristics of the particular raw stock being printed.
Additionally, presently available faders are designed to move only from a completely open position to a completely closed position without stopping at any point in between. However, with new artistic endeavors in the motion picture film industry, it is desirable to provide an exposure control device having the capability, for example, to reduce the intensity of the printing beam and then increase the intensity of the printing beam before reaching a closure point and perhaps continuing this varying of the intensity of the printing beam in a type of sinusoidal or other motion. With an exposure control of the present invention, many currently impossible printing techniques can be developed with movement of the shutter vanes completely controlled rather than simply being movable between an open to a closed position.